Valves are ubiquitous in the downhole drilling and completions industry. As the purpose of valves is to selectively enable fluid communication through the valves, the formation of pressure differentials across valves is customary. Large differential pressures across a valve can not only affect the operation of the valve, but can result in damage to the valve due to the sudden inrush of fluid when the valve is opened. For example, ball valves are often used in the art as so-called barrier valves for at least temporarily shutting off production in a hydrocarbon well, which leads to very large pressure differentials. These large pressure differentials can result in the rotatable ball member of the valve to be pressed firmly against its housing, which causes large frictional forces between the ball and the housing and increased difficulty in opening the valve. The frictional forces and inrush of fluid to the valve when opened can cause damage to the valve such that it does not open, close and/or seal properly. Systems for equalizing pressure before opening barrier and similar valves have been developed, but the industry is always receptive of advances and alternatives in pressure equalization technology.
In view of the potential for large variations of pressure on either side of an equalizer valve when in the closed position, designs have been developed to maintain the valves in a closed position if the pressure on either side of a closed equalizer valve increases. One such design is described in U.S. Pat. No. 9,062,519. This design incorporates three seals two of which are dynamic seals 16 and 18 that define a chamber 46 that is pressurized with a control line 45. Pressure applied in control line 45 overcomes the force of the return spring 50 to move a piston 12 to separate metallic components 30 and 40 at the lower extremity 42 of the assembly. Without pressure applied in line 45 rising pressure at opposed ends of the equalizer valve 14 in regions designated as P1 and P2 will simply force the already closed valve 14 to stay in the closed position. This happens as pressure from P1 communicates to surface 36 which is larger than opposing surface 38 for a net closing force on piston 12. Higher pressure from P2 acts directly on surface 42 to push the piston in a direction that keeps surfaces 30 and 40 together for the closed position of valve 14.
While this design accomplishes the purpose of keeping the equalizer valve closed when it experiences a rise in end pressure at P1 or P2 it leaves the metal to metal seal of surfaces 30 and 40 exposed to velocity effects and associated erosion when the equalizer valve is actuated to open with pressure in line 45. Due to the annular piston design using surface 48 on piston 12 there need to be two opposed seals to define pressure chamber 46. As a result there are three seals required to accomplish the result of keeping the valve in a configuration where pressure increases on opposed ends do not open the valve.
The present invention addresses such issues by using two seals and a flow configuration that allows placement of a metal to metal seal internally to the housing with a tortuous path to reach the metal to metal seal to protect it from erosion when the equalizer valve is actuated to open with a rod piston that bears directly on the movable valve member. Springs can be provided to overcome seal friction in the rod piston actuator. The actuation system is depth insensitive. A plenum covers the lower seal and component configuration is such that pressure from below is conducted to between the dynamic and metal to metal seal while pressure from above is conducted to a back side of a dynamic seal and an uphole side of the metal to metal seal with a net result of a closure force. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.